A retransmission method used for reliable data transmission in a mobile communication system includes Automatic Retransmission Request (ARQ) and Hybrid Automatic Retransmission Request (HARQ). In a conventional mobile communication system, the ARQ and the HARQ are individually used in a data link layer, i.e., a 2nd layer (L2), and a physical layer, i.e., a 1st layer (L1).
The ARQ located in a base station or an upper node has a 1:1 relationship with the ARQ of a user equipment and secures reliable transmission. However, since input SDU of ARQ, includes a packet of a Packet Data Convergence Protocol (PDCP) or Internet Protocol (IP) layer, the SDU is remarkably larger than a transport block (TB) used in an air transmission section. Therefore, there is a problem that a retransmission delay time of the ARQ may become longer than a delay time of a radio section.
To overcome the above problem, the HARQ is introduced in the L1 layer and the transport block of a relatively small size is retransmitted in the L1 layer. Accordingly, an abandonment rate of the SDU due to excess of a delay time can be reduced.
However, since the ARQ and the HARQ are individually retransmitted in different layers, a transmission delay time increases and an inefficient process such as retransmission of data occurs.